1. D/ND alternation in Quenya
Common Eldarin seems to have had a relationship between roots beginning in d– and n͡d, generally resulting in words beginning in l– and n– in Quenya. In Note 25 to Quendi and Eldar (The War of the Jewels, p. 413) it is called a “frequent initial enrichment d > nd“). Such a relationship may help explain the connexion between some words whose etymologies are obscure.
Attested examples of d/n͡d connexions include:

To add to these I suggest the following, which do not have secure etymologies:

!√dū: Q lúna “dark” (PE 17:22) in Lúnaturco and Taras Lúna, both meaning “Dark Tower,” where lúna is clearly equivalent to S dûr in Barad-dûr. Cf. in The Etymologies, entry √doȝ (The Lost Road, p. 354) “dûr dark, sombre; cf. Q lóna dark.” The root of lúna is obviously not √doȝ, however, as –oȝ– cannot > –ū– in Quenya. Also cf. Q lúme “darkness” in the second version of the Markirya poem (The Monsters and the Critics, p. 222, line 28) – though this could conceivably be also from a root √lum. Distinguish Q lóme “night” (< *dōmi, Sauron Defeated p. 302 and PE 17:87), according to PE 17:152, from a root √dom.

It is true that the root √n͡dū is also related to √nū/√unu “down, under”; but that doesn’t preclude a relationship to a root √dū as well.

!√doj: Q loiko “corpse, dead body,” seen as part of the compound loikolíkuma “corpse-candle” in the 2nd Markirya poem (The Monsters and the Critics, p. 222 line 20 and p. 223).

!√n͡͡͡doj: Q !noire “tomb,” seen as part of the compound place-name Noirinan “Valley of the Tombs” (Unfinished Tales p. 166), which obviously contains the element –nan(d) “valley.”

These two words have not as yet (to my knowledge) received explicit etymologies, and formally they are ambiguous and might be totally unrelated; loiko could be from !√doj or !√loj (or even a disyllabic !√dojok or !√lojok, unlikely as those roots seem in form); noire could be from !√n͡͡͡doj or !√noj. The root !√loj is apparently preoccupied — not that that means too much — by √lojo in the sense of “mistake” (PE 17:151). However, the possibility that words for “corpse” and “tomb” (in which corpses are placed) could be related to each other, suggesting a similar origin for both — √doj: *doikō > loiko, √n͡͡͡doj: *n͡͡͡doiri > noire — is an interesting and, I think, attractive one, even if not overwhelmingly convincing.

2. The DD Page
In Parma Eldalamberon #17, p. 150, a page of etymologies is mentioned which the editor has called “DD,” referring to Dalath Dirnen, the name of a region of Beleriand. It includes the roots √dal, √þol , √nakh, √tor, √lewek, √lok, √phaw, √ruth, √serek, and √ruju. This particular combination is unlikely to be random or accidental, but probably reflects a certain set of preoccupations that were on Tolkien’s mind at the time of composition.

√ruju is part of a gloss on the element ruin in Orodruin, which would in this instance be interpreted as “fiery mountain” (Q ruina “blazing, fiery,” PE 17:183).

The other elements, however, are from another branch of the mythology.

√dal is invoked to explain Dalath Dirnen (in the published Silmarillion, “Talath Dirnen”) the Guarded Plain, which is mentioned in the Narn i Chîn Hurin as an area watched by the spies of Nargothrond.

√thol appears in the name Gorthol “Dread Helm,” used by Túrin when he and Beleg patrolled the region around Amon Rûdh, which was called Dor Cúarthol, “Land of Bow and Helm,” which contains the same thol element.

√phaw and √lok combine to explain the word Foalóke, referring to Glaurung, and which seems (in this instance) to mean something like “dragon breathing out a foul breath.”

√ruth explains the name of the sword of King Thingol, Aranrúth “King’s Ire.”

√serek explains the name of the plant seregon, which was found on the slopes of
Amon Rûdh.

√ruju also has a similar connexion: the entry suggests changing the name of
Glaurung to Angruin “Iron Fire.”

It therefore seems highly likely that in writing this page, Tolkien was thinking about — possibly had been recently rereading or rewriting — the Narn i Chîn Húrin, and particularly the section in which Turin abides among the outlaws at Amon Rûdh. In the stand-alone Children of Hurin (2007), Aranrúth appears on p. 96, Talath Dirnen on p. 110, seregon on p. 128, Dor-Cúarthol and Gorthol on p. 146. Foalóke is an old epithet for Glaurung that goes back to the Book of Lost Tales, later abandoned (the related word Urulóke “Fire-dragon” is used of Glaurung instead); its reappearance here may be transitory.

In this context, it is possible to explain the motivation for the creation of the root √nakh “narrow, thin.” PE 17:166 gives the following derivatives, all Quenya: náha “narrow”; nahta (verb) “confine, oppress”; and (a)nakka “narrows, defile, pass, cut.” None of these words appears, as far as I know, elsewhere in Quenya; the verb nahta– does appear, but with a different sense and etymology, with the meaning “slay” (VT 49:24) from the root √n͡͡͡dak. However, considering the Sindarin forms that would correspond to the Quenya, it becomes possible to explain what this root is doing on this page and why it was created. Q náha would correspond to S !nauch; Q nahta– to S !naetha-; and Q (a)nakka to S !(a)nach.

(A)nakka means, among other things, “a pass,” and one of the geographical features of the Narn i Chîn Húrin is the Pass of Anach, by which a road crosses the Ered Gorgoroth from Taur-nu-Fuin into Dimbar. On p. 142 of The Children of Húrin, Orcs cross the pass of Anach and seize Dimbar; and on p. 151, Beleg pursues Orcs through the pass of Anach into Taur-nu-Fuin and there finds Gwindor. These events take place in the same section of the Narn, during and immediately after the story of Beleg and Turin in Dor-Cúarthol. It seems most likely, therefore, that the Q word (a)nakka and its root √nakh were created to explain the meaning of the S name Anach, even though the name is not actually cited on the DD page.

3. Minaþurie
The word minaþurie appears in Tolkien’s essay on the river names of Gondor (Vinyar Tengwar 42:17). It is there given as part of the name of an (imaginary) Gondorian record titled Ondonóre Nómesseron Minaþurie. This is translated as “Enquiry into the Place-names of Gondor” (though more literally it should be translated as “‘enquiry’ of Gondor-toponyms”). The word minaþurie is adequately analyzed in the editor’s note #39 — though mina could only mean “into” (of which it is a near-exact calque, mi “(with)in” + na “to”) and not “in” in its static sense; and the assumption that the whole word must be an exact calque on Latin inquirere is perhaps unwarranted.

No explanation of the form of the base þur– is offered by the editor. He notes that in The Etymologies, √thur means “surround” or “secrete” (i.e., in the sense of “hide” or “make secret,” not in the biological sense). Although some of the etymologies for which √thur is invoked are probably obsolete, it seems to be preserved in the names Thurin “secret,” Thuringud “hidden foe,” Thuringwethil “woman of secret shadow.” This root, however, makes no sense as a base for the word minaþurie: an “enquiry” cannot be a “making secret,” exactly the reverse of its meaning.

A root of the form √thur is not, however, the only possible basis for the Quenya base þur-. Quenya þ- could arise from either Quendian *tʰ- or *st-; Quenya –r– could arise from either –r-, –s-, or –d-. There is a root √thus in the Etymologies which, however, means “foul” or “corrupt”; it was probably made obsolete by the later root √thaw “detestable,” as both are invoked to explain the Quenya word saura “bad, foul.” √thus could also be an extension of √thu (as √sus of √su) meaning “breathe.” Neither of these can explain þur-.

There are no attested roots of the forms √stur or √stus. That leaves √stud/√thud, the root of the Quenya words sunda “root” (as of a tree or a mountain), sundo “base” or “root” (of a word), and Sindarin thond (< *thundā) “root,” as in the name of the river Morthond “Blackroot” (Appendix E). In The Etymologies this root appears as √sud “base, ground,” later altered to √stud (VT 46:16). As far as the attested derivatives go, the root might as well be √thud. Although roots beginning with st occasionally appear with –st– in Quenya compounds (e.g. Elestirne, Carnistir, aristorna), **-stunda- does not appear in Tarmasundar “roots of the pillar” — though I wouldn’t really expect it to.

A noun meaning “root” could come from several possible verbal concepts: it could be something that “supports” or “upholds,” with regard to what is above it; it could be something which “is at the bottom,” with regard to its position; or it could be something which “penetrates downward” or “delves,” with regard to what is below it. The last two would adequately explain the Q verbal stem þur– and the word minaþurie. An “enquiry” could easily be a “delving into” (or a “rooting into”!). It could also, somewhat less probably, be a (looking) “into the base.” In the context of the imaginary essay, the author is looking for the “bases” on which the Gondorian toponyms are founded.

I propose, therefore, that þurie (surie) is from *tʰudijē, the infinitive of a verbal stem *tʰud-, meaning something like “go down to the root,” from which the nouns sundo and sunda also derive.

4. Queren
I originally thought that the word !queren — cited as querend-, and defined as “pivot,” “revolving centre” (PE 17 p. 65) — was an agental formation directly from the verbal stem √kwer “turn” (attested in The Lord of the Rings in the word nuquerna “upside-down,” i.e. “turned down”). But that is surely wrong; such a form (meaning “one who turns”) would have to be !querindo. In light of the definition “revolving centre,” I suppose it’s more likely that the word combines the stem quer– and a shortened form of the word ende “center.”

5. Ringarë
I had assumed that the month name Ringare (approximately December) — which obviously contains ringa “cold” — meant something like “cold day” (on the model of yestare, mettare, cormare). This is of course formally possible, but it faces the basic problem in meaning that a month is not a day; and since a ré is one entire 24-hour day, one can’t even finesse the point by saying that it means “the month with cold days,” i.e., “the month when it is cold (even) in daylight.”

I wonder, then, whether it might also contain the abstract suffix -(a)re, seen in almare “blessings, blessedness” (found under the root √gala in The Etymologies); and perhaps cf. also fanyare “the skies… the upper airs and clouds” (Markirya) < fanya “cloud.” The meaning then might be something like “coldness, chill.” Almare in The Etymologies is equivalent to almie (with the Quenya suffix –ie, which produces more-or-less abstract nouns of quality derived from nouns and adjectives (like English -ness, -hood, -ship, -ity: e.g. tára “high,” tárie “height”); so perhaps ringare is equivalent to !ringie. The Sindarin equivalent is not much help; it is Girithron, girith “shivering” + raun (<*rānā) “moon, month.”